1. Field of the Invention
The present invention generally relates to a keyboard and a membrane switch for a keyboard, and more particularly to, for example, a wireless type keyboard and a membrane switch for a wireless type keyboard.
2. Description of the Related Art
Keyboards which are used as input devices for computers include a type having a keyboard connected to a computer with a cord or the like and a wireless type having, for example, a built-in transmission circuit and an antenna for performing wireless communications with a computer.
The wireless type keyboards have different transmission distances depending on the transmission circuit of the wireless keyboard. For example, there are long distance type wireless keyboards transmitting data (signals) at long distances (e.g. several tens of meters) and short distance type wireless keyboards transmitting data (signals) at short distances (e.g. no more than ten meters). The long distance type wireless keyboards are mainly used outdoors and the short distance type wireless keyboards are mainly used indoors (e.g. inside the house or office).
The conventional short distance type wireless keyboard uses radio waves in a narrow bandwidth and has a center frequency of approximately 300 MHz. The short distance type wireless keyboard includes a rod-shaped antenna. Since the rod-shaped antenna occupies a large amount of the small space inside the keyboard, only a single antenna can be installed in the keyboard.
The conventional short distance type wireless keyboard has two problems. The first problem is that the data transmission speed is insufficient due to the narrow bandwidth of the radio waves. The second problem is that fading may be caused by the environment surrounding the keyboard since only a single antenna can be installed in the keyboard. This results in low reliability in the data transmission from the keyboard to the main body of the computer.